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Australia/Lord_Howe is the weirdest timezone

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Re: Australia/Lord_Howe is the weirdest timezone

#341

Post by krick »

Maxamillion96 wrote: post #215
wakahiu wrote: post #180

Earlier quoted context omitted.

This is common across East Africa, including Kenya where I’m from. The night ends at 6:00AM, with 7:00AM being saa moja (first hour) of the day. Similarly, the day ends at 6:00PM (thenashara). Intuitively, this clock makes much more sense than the English clock. There’s rarely confusion between times because it’s embedded in the language.

Same with Somali. The first hour of daylight is hal saac (Hour 1) 7 AM is 1 Saac ( Hour 1) 6 PM is 12 Saac ( Hour 12) 7 PM is 1 Saac 6 AM is 12 Saac

> 7 AM is 1 Saac

> 7 PM is 1 Saac

How do you distinguish AM/PM? How does one say that something will happen 19:00 specifically, and not 07:00?

Re: Australia/Lord_Howe is the weirdest timezone

#342

Post by iso8859-1 »

aleksi wrote: post #99

The most interesting timezone I ever encountered is Europe/Moscow on and around January 1, 1900. If you decide to use that date as a zero date in your code (for example, to handle the transition from two digits per year), you will be in a lot of pain: the offset was +02:30:17. Yes, with 17 seconds! Demo: https://go.dev/play/p/lq36Plr1sIL

The tzdb assumes Local Mean Time (LMT) was used all over. For example, the tzdb has Africa/Monrovia still using LMT in 1970.

https://en.wikipedia.org/wiki/Local_mean_time

Re: Australia/Lord_Howe is the weirdest timezone

#343

Post by wbl »

noleary wrote: post #316
sebastialonso wrote: post #213

Related to the subject, can anyone recommend a book about timezones? Not a technical, programming book, but one with the history of time zones and curious use cases?

It is not exactly what you're looking for, but long ago I read this book about the invention of the naval chronometer: https://en.m.wikipedia.org/wiki/Longitude_(book) It's generally pretty well-regarded and closely related.

Revolution in Time is drier but still interesting and covers up past the quartz crisis starting from Babylon.

Re: Australia/Lord_Howe is the weirdest timezone

#344

Post by ucarion »

hprotagonist wrote: post #96
guidedlight wrote: post #18

Nah, the weirdest time zone is Africa/Addis_Ababa, which nobody in Ethiopia follows. Instead the locals offset the time by 6 hours. So the AM cycle starts at dawn (i.e. 6am), and the PM cycle starts at dusk (i.e. 6pm). https://en.wikipedia.org/wiki/Time_in_Ethiopia

Ethiopian time keeping is peculiar all over. https://en.wikipedia.org/wiki/Ethiopian_calendar The Ethiopian calendar has twelve months, all thirty days long, and five or six epagomenal days, which form a thirteenth month.

Almost every calendar system has a similar trick: https://en.wikipedia.org/wiki/Intercalation_(timekeeping)

The west inherits from the Romans, and Julius Caesar standardized away the Roman intercalary month by glomming it into Feburary. Before that a "priest" (the pontifex maximus) (in scare-quotes because it was a political office) would add that month on an ad-hoc basis. Not so different!

Re: Australia/Lord_Howe is the weirdest timezone

#345

Post by krick »

alserio wrote: post #257
nine_k wrote: post #202

Earlier quoted context omitted.

This is indeed a more logical clock, as it follows the natural cycle of activity. Equally, calendars that put the end of the year at the time after harvest ("autumn"), or at the start of agricultural work ("spring") are also more logical. Positioning the beginning of a new day at noon, and a new year t a solstice, is just a technical convenience, because these are easy to detect with very simple astronomy tools.

didn't the julian/gregorian calendar started that way and drifted?

Of course not. Gregorian Calendar didn't drift, it just fixed drift in Julian calendar, which was like a couple of weeks by 1582. And "new year" in Julian calendar was 1st of January, same as now. It was inherited from previous Roman tradition, because Romans already had the custom to mark 1st of January as a new year, because since 153 BCE it was the date when consuls were inaugurated. So it's an entirely political thing and makes no real sense whatsoever. We are celebrating the day of Roman consulate inauguration for more than 2000 years now.

And before that they they started years from 1st of March, which is much closer to one of the Equinoxes, which is what all sane people (including french revolutionaries) consider to be the proper start of a year.

Re: Australia/Lord_Howe is the weirdest timezone

#346

Post by ajanuary »

ChrisMarshallNY wrote: post #55

I’ve found the best way to deal with TZ conversions, is to use UTC as a common fulcrum. I convert the target TZ to UTC, using my local utility, then use my local TZ utility to convert from UTC to local. But I write iOS software, so I have very solid local tools at hand. It might be more problematic, on, say, a webserver. On a related note, I wrote this utility[0], some time ago. It uses the TZ map from the TZ Boundar…

You need to be careful with some circumstances. I recently had to fix up a case where someone had tried this with a recurring local date. Something needed to happen at 4am local time every day. They had converted 4am local time to UTC based on the timezone offset on the day the config was saved. This then restored incorrectly when the timezone offset changed because e.g. a DST transition.

Re: Australia/Lord_Howe is the weirdest timezone

#347

Post by autarch »

Lance_ET_Compte wrote: post #273

A thousand years ago, every village had their own timekeeping and it worked. Our village is now earth. What if we just abandoned daylight-savings time and timezones and just went with GMT (or anything else) for everywhere on earth? There would be cultural effects as people in California now start work at 16:00, for example...

Time zones _without_ DST would be relatively easy to deal with. The answer is not "abolish time zones", it's just "abolish DST".

Re: Australia/Lord_Howe is the weirdest timezone

#348

Post by autarch »

> It’s not like programming languages support representing 61-second minutes anyway

This is not true. Someone already noted that Raku supports leap seconds. I think this may be partly my fault, because Perl 5's most popular datetime library, `DateTime.pm`, supports leap seconds.

It's my fault because I created `DateTime.pm` and implemented its leap seconds support. In retrospect, this was almost certainly a mistake. Almost no one cares about leap seconds. It just produces all sorts of weird confusion. Like why does adding 60 seconds produce a different result than adding 1 minute, but only rarely?

And it makes the code _way_ more complicated, especially since I wanted to validate whether setting second to 60 was valid.

This seems simple. Why not just look up the leap second table and check? Well, the `DateTime` constructor takes time components (including `second => 60`) and _any_ time zone. So we have to convert the date/time passed to the constructor to UTC in order to do that lookup. But doing that conversion ... ended up involving values that include leap seconds because of historical reasons.

It's a huge mess for very little gain.

As to Raku, I think it's stdlib datetime library borrowed from Perl 5's `DateTime.pm` quite heavily so it inherits some of the same bad design decisions.

Re: Australia/Lord_Howe is the weirdest timezone

#349

Post by foobarchu »

apelapan wrote: post #132
hocuspocus wrote: post #91

Earlier quoted context omitted.

> The naive way to do so would be via a static mapping of state to time zone but there are a few edge cases that preclude doing this More than a few, state is really the wrong resolution here, US timezones follow counties and native reservations borders. ZIP codes should probably be good enough but I'd be careful too. If your volume of addresses isn't too crazy, the robust way is to reverse geocode them and use a lib…

There used to be at least one airport in a tribal area in the US, that had the timezone of the reservation (not same as state) but the DST of the surrounding state (not same as reservation). Can't remember the code for it now, had a lot of interesting timezone issues in a previous job.

My favorite is the hopi reservation, which does not observe DST and exists entirely inside of the Navajo reservation, which does observe it, and which exists entirely within Arizona, which again does not observe DST, and exists entirely within the United States which does observe DST in the general case.

Re: Australia/Lord_Howe is the weirdest timezone

#350

Post by eikenberry »

kccqzy wrote: post #286

The most amusing tidbit about the tz database is that it contains an estimate of Big Bang, and it refuses to calculate timezone transitions occurring before the Big Bang. The commit message at https://github.com/eggert/tz/commit/b22d459a367f4d01b10f6f6b... says: > For example, Glib computes Sao Paulo time stamps as if Brazil's circa-1913 rules were still in effect. (Thanks to Leonardo Chiquitto for reporting the bug.…

That's a fun easter egg in the TZ database. I'd never heard of it, but how often do you need to calculate TZ data that old. Hopefully we'll be done with time zone's completely before the theory is outdated.
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